New research probes relationship between poverty, stress, and intelligence

“Family income is a strong and consistent predictor,” of test scores, school grades and education, say a Cornell University study in the current Proceedings of the National Academy of Sciences journal. “The longer the childhood exposure to poverty, the worse the achievement levels become.”

Although a “large, robust literature” stretching back more than a decade describes this observation, study authors Gary Evans and Michelle Schamberg note there is no biological explanation for it. Why does poverty have this effect?

To find an answer, the pair looked at 195 men who were part of a long-term study of rural poverty. The study included health records and income. In 2006, about 22% of all children nationwide lived below the poverty line, living on less than $21,200 for a family of four, according to the federal Department of Health and Human Services. (About 18% of people worldwide live below the international poverty line of $1 a day, according to Princeton economist Alan Krueger.)

“The proportion of early childhood spent in poverty is also significantly related to working memory,” finds the study, perhaps not surprising. But when the researchers went back and looked at the men’s health records, the relationship between poverty and memory dissolved, revealing their health — as reflected in blood pressure, obesity and stress hormone measures — are factored in. What looks like an income effect is actually a public health problem.